Cooling device for a motor vehicle

ABSTRACT

The invention relates to a cooling device ( 1 ) for a motor vehicle with a combustion engine ( 2 ) comprising a coolant radiator ( 5 ) through which air can flow, an axial blower ( 3 ) which is arranged behind the coolant radiator ( 5 ) in the airflow direction (L), [and] a shroud ( 6 ), arranged between the coolant radiator ( 5 ) and the axial blower ( 3 ), with a shroud ring ( 7 ) in which the axial blower ( 3, 3   b ) is arranged so it can turn. 
     It is proposed to widen the shroud ring ( 7 ) on the air outflow side radially into a flow guidance device ( 8 ).

The invention relates to a cooling device for a motor vehicle according to the preamble of claim 1.

Known from the applicant's DE 33 04 297 C2 is a cooling device for motor vehicles with an axial blower, which is engine-mounted and can be driven by the combustion engine of the motor vehicle. The axial blower sucks in air through a coolant radiator, to the back side of which is attached a radiator shroud for channeling the air flow. The axial blower has an axial blade attachment with an external guide ring (shell), which projects against the flow direction beyond the front edges of the blade, and extends into an engine-mounted inlet nozzle. As a result of this combination of an inlet nozzle and a projecting guide ring, an annular gap with a 180° direction change is created that produces a strongly throttled gap air flow. The guide ring is radially enlarged in its downstream area, and it can also additionally have a diffuser part. Because of a strong throttling, the axial blower has a semiaxial flow, which is supported, or reinforced, by the enlarged area of the guide ring and diffuser part. As a result of the incorporation of the axial blower in the vicinity of the motor, recirculation of the exiting air flow can occur in the known arrangement, i.e., a renewed aspiration through the radiator can occur that detrimentally affects the cooling capacity.

Known from DE 42 22 264 A1 is a cooling device for a motor vehicle that has an electrofan, i.e., a fan that is driven by an electromotor. In this known construction design, the electromotor and the axial blower (axial fan) are attached by braces, a shroud ring, and a radiator shroud on the radiator side. The shroud ring has a cylindrical part in which the axial blower rotates, and a diffuse, flaring surface which is connected to the cylindrical part downstream of it. Other data regarding the design, the dimensions, and the purpose of the diffuse flaring surface are included in the patent. In accordance with the representation provided in the drawing, the person skilled in the art will therefore start with a conventional diffuser with a flare angle of approximately 7° relative the axial direction. This means that the outflow of the air behind the axial blower is oriented axially, i.e., no deflection occurred, only a deceleration of the flow.

The problem of the present invention is to improve the blower characteristics of a cooling device of the type described in the introduction, and also to prevent the recirculation of the air flow exiting from the fan.

This problem is solved by the characteristics of Claim 1. According to the invention, the shroud ring widens radially on the side of the outflow into a funnel-shaped flow guidance device. The flow exiting from the fan, which is a semiaxial or semiradial flow (flow with an axial and with a radial component), is further deflected by the flow guidance device outward, i.e., in the radial direction. This prevents the outflow behind the fan from frontally hitting the engine block and other units behind the fan, and collecting there. As a result of the radial deflection of the flow, a recirculation, i.e., a reentry of the air flow into the radiator, is also prevented, which improves the cooling capacity.

Advantageous embodiments of the invention can be obtained from the dependent claims. The radial widening of the flow guidance device is characterized by a flare angle which is at least 55°, preferably 60° and more, with respect to the axial direction. The radial expansion can occur in one step, by means of a conical surface with a flare angle, or in at least two steps, by at least two successive connected conical surfaces with increasing flare angles or in the shape of a flare or bell. As a result, a relatively strong expansion occurs, which reinforces the semiradial flow in the fan further in the radial direction. Thus a relatively strong deflection is achieved in a relatively short axial installation space. The flare angle α can also be designed to be variable over the circumference, if the outflow conditions behind the fan vary, for example, because of secondary units arranged on the combustion engine.

The flow guidance device is advantageously characterized by a maximum external diameter on the downstream end that is at least 1.1 times, preferably 1.15 times, that of the fan diameter. As a result, a maximum deflection of the outflow can be achieved in the installation space available in the vehicle.

The fan blades can either turn within the cylindrical area of the shroud ring, or they can have a blade overhang on the downstream side that extends into the widened area of the flow guidance device. As a result, the advantage is achieved that the semiaxial flow into the externally located blade areas or blade tip areas is improved, and it contacts directly—without separation—the internal wall of the flow guidance device; the flow is stabilized.

To further improve the fan characteristics, a known inlet nozzle is provided on the double shroud ring that works in cooperation with a guide ring or shell that is attached to the blade tip. As a result, an annular gap and consequently a gap flow with a 180° direction change is produced. The gap flow in the annular gap is directed against the main axial flow in the fan, and it sucks air out of the outflow area. In this context, it is also advantageous that, as a result of the aspiration caused by the gap flow, a greater deceleration is achieved in the outflow area (the effect of boundary layer aspiration).

The semiaxial outflow and the radial deflection of the outflow toward the exterior can be supported by a radially widening shell of the fan, i.e., by a shell which widens like a diffuser. The tendency for the flow to separate is thereby decreased.

According to an advantageous embodiment of the invention, the shroud ring is engine-mounted, i.e., it is fixed to the block of the combustion engine. As a result, relative motions are generated between the shroud and the radiator and between the shroud ring and the shroud, respectively. The relative movements are compensated by flexible or movable sealing means in the form of lips or folded bellows.

The axial blower is also engine-mounted, and it is driven by the combustion engine preferably via a fluid friction clutch. As a result, minimal gaps are formed between the shroud ring and the blower blade tips or the blower shell.

Embodiments of the invention are represented in the drawing and explained in greater detail below. In the drawing

FIG. 1 shows a cooling device according to the invention with an engine-mounted axial blower, and a radiator,

FIG. 2 shows a modified embodiment of the axial blower according to FIG. 1,

FIG. 3 shows an additional embodiment of the cooling device with a ring fan and integrated inlet nozzle, and

FIG. 4 shows an additional embodiment of a flow guidance device with a flare angle α which is variable over the periphery.

FIG. 1 shows a cooling device 1 according to the invention for a motor vehicle, which has an engine block 2 on which an axial blower 3 is attached and positioned. The axial blower 3 has a fan hub 3 a with axial blade attachment 3 b and a rotational axis a. The fan hub 3 a is attached to a fluid friction clutch—not shown—which is driven via a belt drive system 4. (It is also possible to use a direct drive via the crankshaft of the combustion engine.) On the side of the axial blower 3 facing away from the engine block 2 is arranged a coolant/air heat exchanger 5, hereafter called a radiator, which is braced—not shown—against the body of the motor vehicle (for example, the side rails). Relative movements between the radiator 5 and the engine block 2 occur as a result. Air, represented by an arrow L, flows through the radiator 5. On the outflow side, a shroud 6, which is designed in the shape of a bonnet, is connected to the radiator 5, and guides the airflow exiting from the radiator 5 to the axial blower 3. The latter is surrounded by a shroud ring 7, which is designed cylindrically on its internal side, and which is connected, in the downstream direction, to a funnel-shaped widening flow guidance device 8. The shroud ring 7 and the flow guidance device 8 are designed as a unit in the represented embodiment. Arranged on the upstream part of the shroud ring 7 is an elastic lip 7 a which lies against the shroud 6 and can slide on the latter. The shroud ring 7 is attached—not shown—to the engine block 2, while the shroud 6 is attached via an elastic fastening element 6 a to the radiator 5. The fan 3, or its blade attachment 3 b, has an external diameter D_(L). The flow guidance device 8, on its downstream end, has an external diameter D_(A). The two diameters D_(A), D_(L), satisfy the following inequality: 1.1≦D_(A)/D_(L)≦1.4, particularly 1.15≦D_(A)/D_(L). The flow guidance device 8 has a conical surface 8 a which forms an angle α with the axial direction (rotation axis a), this angle characterizing the measure of the radial widening of the guidance flow device 8. This so-called flare angle α is chosen to be greater than 55°, preferably greater than 60°. The geometry of the flow guidance device 8 is determined using the two above-mentioned dimensioning units D_(A)/D_(L) and the flare angle α. The transition from the cylindrical area of the shroud ring 7 to the conical area 8 a is preferably rounded in form, i.e., it promotes flow.

The flow guidance device 8, 8 a according to the invention has the effect that the air flow—represented by a dashed flow arrow P—that exits from the fan 3 b is deflected outward in the radial direction. As a result, on the one hand, an accumulation of the air flow in front of the engine block 2 is prevented, and on the other hand a recirculation, i.e., a return flow in the direction of the radiator inlet 5, is also prevented.

FIG. 2 shows a cooling device 9, similar to the cooling device of 1 FIG. 1, except that it has an axial blower 10 which is modified or axially offset with a hub 10 a and an axial blade attachment 10 b. The blades 10 b have a blade overhang ü in the airflow direction with respect to the cylindrical part of the frame i.e., the blades 10 b extend with their overhang ü into the radially widened conical area 8 a of the flow guidance device 8. The course of the semiaxial flow over the blades 10 b, and the outflow in the area of the flow guidance device 8 are represented by a dashed flow arrow S. This variant with the blade overhang u promotes a low-loss outflow with subsequent radial deflection, and stabilizes the flow.

FIG. 3 shows, as an additional embodiment of the invention, a cooling device 11 in which a shroud 12, a shroud ring 13, and a flow guidance device 14 are formed as a single plastic injection-molded piece. In addition, an inlet nozzle 15 is overmolded in the inlet area of the shroud ring 13, as described in a similar form in the state of the art mentioned in the introduction. The axial blower 16 is designed as a so-called ring fan, i.e., a shell or guide ring 17 is arranged on the circumference of the blade 16 b and is connected to the blade tips. As is also known from the state of the art, the guide ring 17 has an overhang on the inlet side that extends into the inlet nozzle 15. As a result, a 180° direction change is achieved. The guide ring 17 has a part 17 b on the outflow side which is widened conically and forms a transition to the adjoining flow guidance device 14. An annular gap 18 is thus formed between the guide ring 17 and the shroud ring 13 which develops a gap flow opposite the main flow in the fan. The inlet nozzle 15, in connection with the guide ring 17, improves the flow conditions in the blade tip area, reduces the noise level, and decreases the leakage flow. In addition, the aspiration of the gap flow in the downstream area of the fan results in a greater deceleration of the main flow and a better application of the flow against the flow guidance device 14. The gap flow thus has the known effect of aspiring a boundary layer. For the rest, the cooling device 11 corresponds to the cooling device 1 according to FIG. 1.

The injection molded part which consists of the shroud 12, the shroud ring 13, the flow guidance device 14, and the inlet nozzle 15, is connected by braces, which are not shown, to the engine block 2. Therefore there are practically no relative movements at all between the guide ring 17 and the shroud ring 13, so that a minimal annular gap 18 can be achieved. However, an elastic or movable fastening of the shroud 12 to the radiator 5 is required, and it is preferably achieved using an elastic fastening element 12 a.

In contrast to the embodiments represented in the drawing, which has a conical or cone-shaped surface 8 a of the flow guidance device 8, a bell- or flare-shaped form is also possible and within the scope of the invention.

FIG. 4 shows, as an additional embodiment of the invention, a cooling device 20 with a combustion engine 21 that has several secondary units 22 in the front-end area for example, a coolant pump and a generator that are connected by a belt drive to each other. The front of the combustion engine 21 presents a relatively jagged and irregular design due to the arrangement of the secondary units 22. A driver cab 23 is arranged above the combustion engine 21, which closes off the motor space at the top. In front of the secondary units 22 in the driving direction, an axial blower 3 and a radiator 5, or a cooling module formed from several heat exchangers, are/is arranged. Arranged between the radiator 5 and the axial blower 3 is a shroud 24 with a shroud ring 25 in which the axial blower 3 turns. Connected to the shroud ring 25 is a flow guidance device 26 which, seen over the circumference of the shroud ring 25, has a varying flare angle α: in the drawing, for example, two different flare angles are represented, an upper flare angle α₁ of approximately 90°, and a bottom flare angle α₂ of approximately 55°. The flow guidance device 26 is thus adapted to the different outflow conditions to the rear of the axial blower 3, where the conditions result from the arrangement of the secondary elements 22. A low-resistance outflow of the cooling air is achieved as a result of this variable design of the flare angle α over the circumference. 

1. A cooling device for a motor vehicle with a combustion engine, comprising a coolant radiator through which air can flow, an axial blower which is arranged behind the coolant radiator in the airflow direction (L), a shroud with a shroud ring that is arranged between the coolant radiator and the axial blower, with the axial blower being arranged in the frame ring so that it can turn, wherein the shroud ring is radially widened on the air outflow side into a flow guidance device.
 2. The cooling device according to claim 1, wherein the flow guidance device has a surface that forms a flare angle α with the axis (a) of the axial blower, where α≧55°.
 3. The cooling device according to claim 2, wherein the flow guidance device has a conical surface.
 4. The cooling device according to claim 2, wherein the flare angle α of the flow guidance device, seen over the circumference of the shroud ring, is variable.
 5. The cooling device according to claim 1, wherein the axial blower has an external diameter D_(L), and the flow guidance device has an external diameter D_(A) on the outflow side, where the following relation applies: D_(A)≧1.1 D_(L).
 6. The cooling device according to claim 1, wherein the axial blower has blades that turn within the axial extent of the cylindrical area of the shroud ring.
 7. The cooling device according to claim 1, wherein the axial blower has fan blades with a blade overhang (ü) on the outflow side, where the overhang extends in the axial direction of the flow guidance device.
 8. The cooling device according to claim 1, wherein, on the side against which the air flows, the shroud ring has an inlet nozzle and the axial blower has a shell, and in that an annular gap with a 180° direction change is formed between the inlet nozzle and the shell.
 9. The cooling device according to claim 8, wherein a radially external area of the inlet nozzle transitions into the shroud ring.
 10. The cooling device according to claim 8, wherein the shroud, the inlet nozzle, the shroud ring, and the flow guidance device are designed as one piece.
 11. The cooling device according to claim 8, wherein the shell has a downstream, diffuser-like widened area.
 12. The cooling according to claim 1, wherein at least the shroud ring having the flow guidance device is engine-mounted.
 13. The cooling device according to claim 12, further comprising flexible and/or movable sealing means for compensating relative movement between the shroud and the coolant radiator.
 14. The cooling device according to claim 1, wherein the axial blower is driven by the combustion engine.
 15. The cooling device of claim 2, wherein α≧α°.
 16. The cooling device of claim 4, wherein α has values between α₁≧55° and α₂≦90°.
 17. The cooling device of claim 5, wherein D_(A)≧1.5 D_(L).
 18. The cooling device of claim 10, wherein the one piece is injection molded.
 19. The cooling device of claim 14, wherein the axial blower is driven by a fluid friction clutch. 